1. Field of the Invention
This invention relates generally to an ink feed measuring device, and more specifically to an ink feed measuring device wherein a luminous plate and a light receiving plate are disposed so as to closely contact with each other, and the amount of light transmitted through a photographic negative film (or a positive film . . . hereinafter referred to as a film) of a newspaper held between the luminous and light receiving plates is measured by reading out a change in electromotive force generated on the light receiving plate, and a surface source is employed as a light source to ensure uniform brightness on the luminous plate.
2. Description of the Prior Art
In a printing press, for example, a newspaper printing press, which prints a large number of copies at a high speed, a uniform printing finish is strongly desired on each and every sheet of newspaper. However, even in a single page of newspaper, there are some portions where a large amount of ink is required and other portions where a small amount of ink is needed, depending on the nature of news. Therefore, when printing such a newspaper page in succession, supplying the same quantity of ink over the entire page may cause blackening due to overfeeding of ink in some parts and thinning due to shortage of ink in other parts. Consequently, there is a need to control the ink feed amount by measuring the required amount of ink for a given page of newspaper as precisely as possible.
Heretofore, a plurality of incandescent lamps or straight-tube fluorescent lamps have been used as the light source of a measuring device of this type. The luminous plate using these light sources, which are a combination of point or line light sources, tend to be uneven in brightness. In particular, the intensity of illumination on the luminous plate becomes uneven because the use of a plurality of light sources makes a difference in the luminance of individual light sources with the lapse of time. Uneven intensity of illumination on the luminous plate is quite an unwanted phenomenon for a measuring device of this type which controls the feed amount of ink to a printing press with measurements of the change of electromotive force corresponding to the change of the amount of light. Furthermore, incandescent lamps or fluorescent lamps used in such a device are considerably large in size and require appliances or fixtures in some form or other to light them. In addition, since these light sources produce heat, the conventional luminous plates consisting of a plurality of light sources of these types tend to be of large size and have limitations in their construction.